1. FIELD OF THE INVENTION
This invention relates to heat sensitive recording systems for use in facsimile systems and the like, and more particularly it is concerned with a mechanism for positioning a heat sensitive head and a pressing roller relative to each other.
2. DESCRIPTION OF THE PRIOR ART
Facsimile transmission which combines the spontaniety of telephone with the recordability of post has come in recent years to play an increasingly important role in automating business transactions. Facsimile systems now in practical use are broadly divided into two types by the recording system: one type uses an electrostatic recording system and the other type uses a heat sensitive recording system. The heat sensitive recording system offers many advantages over the electrostatic recording system. First of all, the former is free from any danger because no smoke and no odor are produced. The heat sensitive recording sheets are less expensive than the electrostatic recording sheets of the prior art used in facsimile transmission. The heat sensitive recording system requires no developing ink or toner for developing and fixing the images and is superior to the electrostatic recording system in maintenance and reliability in performance. Moreover, the former is more economical than the latter because no expendables to recording sheets are required.
A heat sensitive recording system for use in a facsimile system, for example, comprises a heat sensitive head including a narrow heat generating resistance layer extending in a straight manner on a base plate formed of a heat resistant material of high resistance, and a pressing roller, wherein a heat sensitive recording sheet is held between the heat sensitive head and the pressing roller brought into pressing contact with the heat sensitive head by suitable means, to carry out recording.
In this recording system, it is essential, for obtaining well-defined images of uniform darkness, that the generatrix of the pressing roller be correctly positioned with respect to the resistance layer extending in a straight manner, although it is no less essential that the pressing roller applies pressure to the heat sensitive head with a force uniformly distributed lengthwise of the roller. Thus positioning of the heat sensitive head and the pressing roller relative to each other is a problem that should be solved satisfactorily. On the other hand, facilitation of insertion of a recording sheet between the heat sensitive head and the pressing roller, cleaning of the heat generating resistance layer of the heat sensitive recording head and elimination of possible jamming of the recording sheets makes it necessary to bring the lengthwise surface of the head and the lengthwise surface of the roller out of engagement with each other. Thus the head and roller are supported by separate support means for movement toward and away from each other. As a result, in the prior art, the aforesaid positioning of the heat sensitive recording head and the pressing roller relative to each other cannot be accomplished merely by giving precise finishes to the parts thereof, and it is necessary to adjust the positional relation of the head to the roller at the time of assembling.